The present invention relates, generally, to the evaluation of insulating materials, and more particularly, to vacuum insulation panels, as may be used for various temperature-sensitive products, that are configured to enable the evaluation of the expected performance and integrity of the vacuum insulation panels.
With the rapid world-wide growth in the demand for the shipment and handling of temperature sensitive products, such as blood, food, pharmaceuticals, vaccines, bioengineered products and the like, the need for inexpensive and yet more thermally efficient shipping containers continues to increase dramatically.
In designing and manufacturing insulated shipping containers, various factors must be considered, including weight, size and durability. Since many of the products must be shipped at great distances by rail, truck or air travel, the designers of these containers must strive to keep the weight of these containers at a minimum and yet still provide sufficient protection of the goods at the desired temperature for extended periods, e.g., by providing containers with a sufficiently thick layer of insulation.
In addition, due to the volume of the goods to be shipped, as well as limitations in available cargo space, the size and configuration of the shipping container must be optimized to maintain the desired temperature and yet minimize the area required for storage. Further, the freight and shipping industry has established pricing regulations, known as dimensional weight regulations, that apply to shipping containers which are larger and yet lighter in shipping weight. For example, it can be generally more expensive to ship containers that have an outside dimension of 24xe2x80x3xc3x9724xe2x80x3xc3x9724xe2x80x3 and a weight of 40 pounds than it is to ship containers that have an outside dimension of 12xe2x80x3xc3x9712xe2x80x3xc3x9712xe2x80x3 and a weight of 50 or 60 pounds. Still further, although the minimization of weight and size are desirable design considerations, on the other hand, designers must strive to balance these factors with the need to provide shipping containers that are reusable or can withstand physical impacts or collisions during the shipment of the goods.
As a result of these factors, many of today""s shipping containers utilize combinations of inexpensive paperboard boxes and more costly foam insulating materials, such as, for example, polyurethane, polystyrene or the like. Although these materials combine to provide a low-cost insulating container, because these materials typically attempt to trap gases to reduce heat transfer, these materials typically provide a low insulation value, such as R-7 per inch or lower. However, as regulatory agencies continue to enact more stringent regulations for the temperature control of perishable and other temperature-sensitive goods, such as during the transporting or storing of the goods, the need for more reliable and efficient insulating materials continues to grow. As such, the use of vacuum insulation panels (VIP""s) is becoming more and more predominant in industry.
Vacuum insulation panels are very efficient in providing insulating protection for temperature-sensitive goods and products. Unlike the traditional insulating materials described above, vacuum insulation materials operate by evacuating or removing the gas molecules that transfer heat within the insulating material.
With reference to FIG. 1, a vacuum insulation panel 100 generally comprises a thin, barrier film 102 that is designed to encapsulate a filler core material 106. Barrier film 102 generally comprises a thin material, such as, a metal foil or metalized film laminate, designed to maintain a vacuum within panel 100. Meanwhile, core material 106 generally comprises an open-cell material designed to provide a physical structure to panel 100, to facilitate the drawing of a vacuum from within panel 100, including vacuum area 104, and to inhibit the transmission of heat through panel 100. After drawing the vacuum within panel 100, barrier film 102 is typically sealed to maintain and hold the vacuum for a prolonged period of time. As a result, vacuum insulation panel 100 can provide approximately three times or more the insulation thermal efficiency, e.g., an R-30 per inch insulation value, than that of traditional products with the same wall thickness.
Although these vacuum insulation panels 100 are durable, often lasting two years or more, barrier film 102 is susceptible to deterioration, puncture, tear and other wear that can cause panel 100 to lose the vacuum within barrier film 102 and thus become thermally inefficient for critical temperature applications. Although a detailed visual inspection may lead an evaluator of the panels to a determination as to the integrity of the vacuum within panel 100, generally only the largely visible punctures or tears may be visible. Accordingly, because various of the defects are not readily detectable, damaged vacuum insulation panels currently have the potential to be reused, and thus the potential exposure to the environment for the temperature-sensitive goods is increased. Thus a strong need exists for a vacuum insulation panel that is configured to facilitate an effective inspection and evaluation of the integrity of the vacuum insulation panel.
A vacuum insulation panel according to the present invention addresses many of the shortcomings of the prior art. In accordance with the present invention, a vacuum insulation panel comprises a barrier film and a core material and a vacuum detection indicator. The vacuum detection indicator is configured to facilitate the evaluation of the integrity of the vacuum within the vacuum insulation panel.
In accordance with one aspect, the vacuum detection indicator comprises a cavity in the core material which allows the barrier material to form into a depression when a vacuum is drawn within the panel. As the vacuum is reduced or lost, the depression formed in the barrier material will be similarly reduced or lost.
In accordance with another aspect, the vacuum detection indicator may comprise a viewing window configured above the barrier material to permit the evaluator to readily determine whether the vacuum has been reduced or lost.
In accordance with another aspect, the vacuum detection indicator may comprise a spring-like device configured within the cavity. Upon a reduction in the vacuum with the panel, the spring-like device suitably uncoils to urge the barrier material towards the outer surface of the panel, i.e., the barrier material returns to its original configuration before the vacuum was drawn in the panel.
In accordance with yet another aspect, the vacuum detection indicator may also comprise various other features for indicating when the vacuum has been reduced or lost within the panel. In accordance with this aspect, the vacuum detection indicator may comprise of electrical contacts suitably configured to indicate that the barrier material has been returned to its original configuration, e.g., by providing a closed circuit when the barrier material interfaces with the contacts which can be readily measured or utilized. Further, the vacuum detection indicator may comprise a fluid device configured to release colored-dyes upon loss of vacuum, and which can provide a clearly visible indication of the loss of vacuum within the panel. Still further, the vacuum detection indicators may comprise small mechanical devices of even color indicators, for example, devices which in the presence of gasses either show a mechanical (e.g., a bar scale) change or a color change.